Mine roof supports

ABSTRACT

A mine roof support has a hydraulic leg-aligning device which on pressurization assumes an extension intermediate full and zero extension and which is positively connected so as to push and pull the leg as required. The device may be double-acting piston and cylinder with means for injecting pressure fluid to make up the quantity of fluid in each end of the cylinder to a respective predetermined amount. Alternatively the device may comprise a hydraulically extensible member and a hydraulically contractable member so that on pressurization the first fully extends and the second fully contracts. The two are connected in series mechanically.

United States Patent 11 Claims, 4 Drawing Figs.

61/451), 248/357 E2ld 15/44 61/45.2;

[56] References Cited UNITED STATES PATENTS 2,714,505 8/1955 Joy 61/45 2,859,022 11/1958 Frye 61/45 3,169,377 2/1965 Hoffmann 61/45 3,186,178 6/1965 Allen 61/45 3,192,722 7/1965 Herrmann et a]... 61/45 3,218,812 11/1965 Wilkenloh 61/45 3,324,664 6/1967 Allen 61/45 3,437,010 4/1969 Jacobi etal 91/189 Primary Examiner-Dennis L. Taylor Atmrney-lmirie and Smiley ABSTRACT: A mine roofsupport has a hydraulic leg-aligning device which on pressurization assumes an extension intermediate full and zero extension and which is positively connected so as to push and pull the leg as required. The device may be double-acting piston and cylinder with means for injecting pressure fluid to make up the quantity of fluid in each end of the cylinder to a respective predetermined amount. Al-

' ternatively the device may comprise a hydraulically extensible member and a hydraulically contractable member so that on pressurization the first fully extends and the second fully contracts. The two are connected in series mechanically.

The invention concerns a mine roof support with a leg or prop (hereinafter referred to as a leg)-which is movably fixed at the bottom of a box-type base and bears a roof bar device which rest against the roof. Between one or several of the legs on one hand, and one sidewall'of the box-type base on the other hand, an aligning device is provided to enable the leg or legs to adjust themselves into a freestanding position perpendicular or inclined relative to the strata.

Such alignment devices used with self-advancing mine roof support elements serve to bring the legs of the support element during the advancing operation, i.e. while the legs are released from between roof and floor, into a particular position relative to the box-type base, to which they are movably fixed. A movable connection between box-type base and leg is necessary, so that the leg can avoid the large forces which can be caused by convergence between roof and floor surfaces or by sliding movement of the roof. These forces are large enough to destroy the legs if a rigid connection between legs and box-type-base is use Resilient support arrangements are mainly used to realign a leg back into its ideal position when it is retracted. Resiliency alone however is not always sufficient to bring the leg again into its desired freestanding position, especially when the support element is to be advanced partly underload, as is desirable for a better roof control. in this specification freestanding position is used to mean that position which would be assumed by a leg if no forces were applied to the leg other than those applied by the aligning device which is also the position assumed if the force generated by the aligning device completely overrides any other forces on the leg under partial load conditions.

For this reason it has been proposed to put a hydraulic pressure-aligning ram between the box-type base and one or several legs. This ram brings the legs into the desired position during the advancing operation and keeps them in this position. Such a hydraulic pressure ram can createconsiderably greater forces than the resilient support arrangement used so far for this purpose. The proposed aligning rams are not normally positively connected to the box-type base on one hand and to the leg on the other hand but merely push them apart so that strata forces cannot over extend and thereby damage them. For this reason such an aligning ram can cause movement of the leg only in one direction. Separate rams have to be used to give aligning forces in the direction of the coal face, and aligning forces towards the stowage. These rams would have to be on opposite sides of the leg and this is very unfavorable, as the track on the coal face side of the stowage side row of legs becomes considerably narrower.

It is therefore the task of the invention to create an aligning device for the legs of anadvancing mine support element which cooperates with the leg to be aligned on one side only, which is able to efi'ect the aligning forces on to the legs in two opposite directions and which can yield in response to strata forces in either direction.

According to one aspect of the present invention there is provided a mine roof support'having a leg-aligning device comprising a hydraulically extensible and hydraulically contractabledevice connected to the leg andto, say, the-base of the support in which the device is arranged on pressurization to adopt in intermediate position.

According to another aspect of the present invention there is provided a mine roof support having a leg aligning device in the form of a piston and cylinder device having inlet means for pressure fluid to extend and contract it so that it takes up an intermediate position between maximum extension and maximum contraction and means whereby it may extend or contract on tilting of the leg by forces applied tothe leg.

tion. After'switching off the pressure medium supply to the aligning device, the leg can move in both directions to conform to movements of the roof or other strata movements relative to the box-type base. Damage to the aligning device through these forces is thus excluded. Furthermore, the aligning device acts on the leg from one side only and can be positively connected with it.

According to a special preferred version of the invention two hydraulic pressure rams forming the aligning device are arranged concentrically inside each other, the piston rod of the outer pressure ram being hollow and acting as a cylinder for the inner pressure ram. This provides a particularly solid construction of the aligning device. Besides, tensile and compression forces can, in the case of this arrangement of the pressure rams. influence the aligning device only in an axial direction.

With this version of the aligning device it is particularly useful, if the device for the pressure medium supply is connected with an annular chamber between the cylinder of the outer pressure ram and its piston rod, and if this annular chamber for the pressure medium supply of the surface of the inner piston is connected through a supply line with the pressure chamber of the inner pressure ram. This has the advantage that the entire aligning device needs only a single external pressure medium connection.

lt is also useful, in the case of a concentric arrangement of the two hydraulic pressure rams, if the cylinder of the outer pressure ram is connected with the sidewall of the box-type base serving as abutment, while the piston rod of the inner pressure ram is connected with the leg.

A further possible version of the invention provides, that two cylinders are connected together and the piston in one cylinder is connected with the sidewall of the box-type base, and the piston in the other cylinder is connected with the leg. The pressure medium is supplied simultaneously to the two cylinders.

For alteration of the freestanding angular position of the leg abutment pins are provided in the pressure rams to limit the strokes of the pistons. These pins can be screwed into the un filled sides of the cylinders of the pressure rams. By means of these stop or abutment pins the retracting and extending distances of the piston rods can be controlled, and thus the position of the legs take up when the aligning deyice is pressurized.

The travel of the pistons can also be controlled by partially filling the nonpressurized ends of the cylinders. Furthermore it is possible to provide, in the connection between legs and aligning device on one hand, and/or in the connection between the aligning ram and the sidewall of the box-type base on the other hand, a bolt arrangement for adjusting the length of the connection.

A further solution of the above task is obtained with a mine roof support with an aligning device for one or several legs, which are fixed at the bottom of a box-type base arranged at the floor and bear together a roof bar device resting against the roof. Between one or several of the legs on one hand, and a sidewall of the box-type base on the other hand, the aligning device is fixed so that it can put the leg or legs into a position. This mine roof support is characterized by the fact, that the aligning device consists of a double-acting hydraulic pressure ram whose two pressure chambers can be loaded with a defined quantity of pressure medium.

Due to the structure of the aligning device, the aligning device has a predetermined len'gthwhen pressurized. At this length the leg to be aligned takesit's desired freestanding posi- The piston of this double-acting pressure ram takes up, in the freestanding position of the leg, suitably an intermediate position between its two end positions in the ram, so that it can be retracted further or extended further in the case of strata movements.

A particularly preferred version of such an aligning device provides, that each of the pressure chambers of the doubleacting hydraulic pressure ram is connected with a supply ram I for injecting a defined quantity of pressure medium. The ram chamber of the supply ram is divided into two partial chambers through which a free position can be displaced. One of these partial chambers of each supply ram is connected with the corresponding pressure chambers of each supply ram is connected with the corresponding pressure chamber of the double-acting hydraulic pressure ram, and the others with'a' pressure medium source. The quantity of pressure medium is determined in such a way, that the free pistons are in an end position when the leg is in the desired free standing position:

This guaranteesthat, through a single pressurization of the two supply rams during the advancing operation; the leg is brought into its desired position. j

Embodiments of the invention will now be described by way of example, with reference the drawings:

FIG. I is a side view of a mine roof support with an aligning device for the legs, 1 v

FIG. 2 illustrates one type of aligning device,

FIG. 3 shows a second type of aligning device, and

FIG. 4 represents a third type ofaligning device.

The specific description shows a box-type base 1 of a mine roof support to which legs 2 are universally articulated. On the legs is mounted a roof bar arrangement 3 underpinning the roof. Between a backwall 4 of the box-type base I and arear one of legs 2, an aligning device 5 is provided which is connected between the leg 2 and the backwall 4.

The preferred version of this aligning device 5 is shown in FIG. 2. It consists of an outer cylinder 6 inside which a piston 7 is arranged. The corresponding piston rod 8 is hollow inside and serves, at thesame, time, as a cylinder for an inner pressure ram, in which there is a piston 8joined to a piston rod 10.

The outer cylinder 6 is connected with the backwall 4 of the box-type base 1 via a connecting device 11. The piston rod 10 of the inner pressure ram is connected to a pull and push the leg 2 via a collar l2. A pressure fluid inlet means 14 isprovided in the cylinder 6'to feed pressure fluid into the annular chamber 13 which is connected with a pressure chamber 15 of the inner pressure ram through connecting ducts 16 which are arranged inside the body or piston 7. There is also an overpressure valve (not shown) to allow fluid to be forced out. Screw pins 19 and can be screwed into the ram chambers 17 and 18, which are not loaded with pressure, in order to limit the stroke of the two pistons 7 and 9'. One can instead partly fill the ram chambers 17 and 18 with fluid.

A further version not shown in the drawing provides for the extension or shortening of the aligning device in the connection between the aligning device 5 on onehand and the leg 2 and/or the backwall 4, by means of bolt arrangements.

The aligning device shown inFlG. 2 operates as follows:

- Assuming that the leg 2 has diverged from its ideal position, due to strata movements before the starting of the operation of advance, in direction x or y. During this either piston 9 was displaced in direction x, or piston 7 was displaced in direction 3:. Whilst the legs 2 are released from between roof and floor,

the aligning device is pressurized through device 14."Piston 7 is displaced in direction x, until it touches the abutment pins 19 or until the fluid present in the chamber 17 prevents a to the accompanying drawings. In

A further versionof the aligning device is shown in FIG. 3. This aligning device consists of two parallel arranged pressure rams 21 and 22, whose pressure medium inlets 23 and 24 are arranged so that, underpressure, the piston rod of the pressure ram 21 is extended, while the piston rod of the pressure ble-acting pressure ram, whose cylinder 25 is connected to the.

backwall'4'of the box-type base, and whose piston 29 is con- 1 nectedwith the leg via the piston rod 26. Fluid inlet devices formed as hydraulic reservoirs are connected with the pressure chambers 27 and 28 on both sides of the piston 29. The

reservoirs are cylinders 30, 31 in each of which a free piston 4 32 or 33 is arranged to divide each cylinder into two partial chambers 34 and 35, or 36 and 37. The partial chamber 34 of cylinder 30 is connected with the pressure chamber 27 of the double-acting pressure ram, while the partial chamber 36 is connected with the pressure chamber 28 of the double-acting pressure ram. The free pistons and the partial chambers 34 and 36 act as fluid injection rams operated by a pressure medium supply 38 to the partial chambers 35 and 37. The quantity of pressure medium inside the ram chambers 27 and 34 or 28 and 36 connected with each other is determined in-such a way, that the piston 29 and thus the leg 2 have their ideal position when the free pistons 32 and 33 are brought into their end position through pressure supply, i.e. untilthey touch the abutment-39 shown in FIG. 4. Z

If however, due to strata movements a'movement occurs of leg 2 in direction x or direction y, the piston 29 inside the cylinder 25 moves in'one or the other direction, and due to this one of the free pistons 33 and 34 is displaced from its position shown in FIG. 4. During theadvance operation, i.e. when the leg 2 is released from between roof and floor, the pressure supply line 38 is loaded, so that the piston 32 or 33 is brought again into its end position, and the piston 29 again into its desired freestanding position.

Analogously to the above-mentioned versions in this case, too the ideal position of the leg can be influenced through an adjustable limits for the free pistons.

We claim: 1

1. A mine roof support comprising a roof-engaging member, a ground-engaging member, at least one extensible leg therebetween and articulated at its ends to said members, and a pressure-fluid-operable leg-aligning device, the improvements residing in that the device is positively connected at one end to the ground-engaging member, in that the, leg-aligning device is positively connected with the leg so as to move itin opposite directions, and in that the leg-aligning device comprises two 'rnean one of whichonpressurization extends the further movement of the piston 7 in direction x. At th'e'same time pressure fluid enters pressure chamber. 15 through the connecting'lines 16, and displaced the piston 19in dire'ctiony, until it touches the abutment pin 20 .or until the'fluidpresent in the chamber 18 prevents further movement in direction);

when the pistons 7 and 9 are-extended or. retracted against their abutments, then leg 2 is in its intended position relative to the backwall 4 andthe box-typeibasev 1.-In this position the leg 2 is-reextended again-between roof and floor. After that the pressure medium supplyof the aligning device is switched off. If now, due to strata movements. adisplacemeritoccurs of legs 2 in direction x or in direction y, then the aligning device can yield correspondinglyin both directions with fluid "ex pelled through the over pressure valve. Adjustment of the in tended position of the leg 2 can be done by displacing thel:

abutment bolts 10 and 20 suitably, oralte'ring-the quantityo fluid in the chambers 17 and 18.. The bolt arrangement which is not shown in the drawing tcan'bealtered. a

' device, and apressure fluid inlet is arranged simultaneously to pressurize the means with one acting to extend the device and the other to contract it whereby the device assumes a position of intermediate extension on pressurization.

2. A minero f s means is displaceable, th e,two. means serving-simultaneously to inject the contents of ,the reservoirs into theends of the cylinder ,the quantity of fluid in a reservoir and a respective i 1 end being complementary to the quantity of fluid in theo'ther...

reservoir and its 'respective end so that when the reservoirsare emptied substantially into theends of the cylinders the-piston assumes the predetermined intermediate extension.

pport according to claim 1 whereinsaid'. w device c omprisesa double-actingpiston movable in a cylinder and wherein each endf'of the" cylinder has a fluid. inlet con= V 'nected to a fluid reservoir in which .a respective one-of said. I

3. A mine rodf'sirpport accordingto claim.2 wherein the said reservoirs arein the form "of fluid injection rams each.

5 comprising la eyliridercontaining one. of said means in the form of a free piston dividing the cylinder into two partial chambers one of which is connectedto a respective end of the double-acting pistion's cylinder and the other of which is connected in common with the corresponding other partial chamber of the other fluid injection ram to a source of pressure fluid.

4. A niine roof support according to claim 3 wherein the fluid injection rams incorporate adjustable limits for the free pistons whereby to adjust the freestanding position of the leg.

5. A mine roof support comprising a roof-engaging member, a ground-engaging member, at least one extensible leg therebetween and articulated at its ends to said members, and a pressure-fluid-extensible leg-aligning device, the improvements residing in that the device is positively connected at one end to the ground-engaging member and at the other end to the leg so that the device can move the leg in opposite directions, and in that the device comprises a hydraulically extensible means and a hydraulically contractable means connected to a common source of pressure fluid and arranged in mechanical series so that on pressurization the extensible means is fully extended and the contractable means fully contracted whereby the device adopts an intermediate position from which the device can be extended by external force by extending the contractable means and forcibly contracted by contracting the extensible means.

6. A mine roof support according to claim 5 wherein the two means comprise jointly two cylinders which are joined together and a ram piston in each cylinder, the pistons being connected one to the leg and the other to the base of the mine roof support.

7. A mine roof support according to claim 5 wherein the two means comprise jointly a cylinder in which slides a hollow piston which serves as a cylinder for a piston within it.

8. A mine roof support according to claim 6 wherein there are provided stop pins or like abutments to limit the travel of the pistons, these abutments being adjustably mounted in the cylinder wall at the nonpressurized end.

9. A mine roof support according to claim 6 wherein the nonpressurized ends of the cylinders are partially filled with liquid to limit the travel of the piston.

10. A mine roof support according; to claim 1 wherein the leg aligning device has associated with it a bolt arrangement to adjust the freestanding position of the leg.

11. A mine roof support according to claim 7 wherein there are provided stop pins or like abutments to limit the travel of the pistons, these abutments being adjustable mounted in the cylinder wall at the nonpressurized end 

1. A mine roof support comprising a roof-engaging member, a ground-engaging member, at least one extensible leg therebetween and articulated at its ends to said members, and a pressurefluid-operable leg-aligning device, the improvements residing in that the device is positively connected at one end to the groundengaging member, in that the leg-aligning device is positively connected with the leg so as to move it in opposite directions, and in that the leg-aligning device comprises two means, one of which on pressurization extends the device and the other of which on pressurization contracts the device, and a pressure fluid inlet is arranged simultaneously to pressurize the means with one acting to extend the device and the other to contract it whereby the device assumes a position of intermediate extension on pressurization.
 2. A mine roof support according to claim 1 wherein said device comprises a double-acting piston movable in a cylinder and wherein each end of the cylinder has a fluid inlet connected to a fluid reservoir in which a respective one of said means is displaceable, the two means serving simultaneously to inject the contents of the reservoirs into the ends of the cylinder, the quantity of fluid in a reservoir and a respective end being complementary to the quantity of fluid in the other reservoir and its respective end so that when the reservoirs are emptied substantially into the ends of the cylinders the piston assumes the predetermined intermediate extension.
 3. A mine roof support according to claim 2 wherein the said reservoirs are in the form of fluid injection rams each comprising a cylinder containing one of said means in the form of a free piston dividing the cylinder into two partial chambers one of which is connected to a respective end of the double-acting pistion''s cylinder and the other of which is connected in common with the corresponding other partial chamber of the other fluid injection ram to a source of pressure fluid.
 4. A mine roof support according to claim 3 wherein the fluid injection rams incorporate adjustable limits for the free pistons whereby to adjust the freestanding position of the leg.
 5. A mine roof support comprising a roof-engaging member, a ground-engaging member, at least one extensible leg therebetween and articulated at its ends to said members, and a pressure-fluid-extensible leg-aligning device, the improvements residing in that the device is positively connected at one end to the ground-engaging member and at the other end to the leg so that the device can move the leg in opposite directions, and in that the device comprises a hydraulically extensible means and a hydraulically contractable means connected to a common source of pressure fluid and arranged in mechanical series so that on pressurization the extensible means is fully extended and the contractable means fully contracted whereby the device adopts an intermediate position from which the device can be extended by external force by extending the contractable means and forcibly contracted by contracting the extensible means.
 6. A mine roof support according to claim 5 wherein the two means comprise jointly two cylinders which are joined together and a ram piston in each cylinder, the pistons being connected one to the leg and the other to the base of the mine roof support.
 7. A mine roof support according to claim 5 wherein the two means compriSe jointly a cylinder in which slides a hollow piston which serves as a cylinder for a piston within it.
 8. A mine roof support according to claim 6 wherein there are provided stop pins or like abutments to limit the travel of the pistons, these abutments being adjustably mounted in the cylinder wall at the nonpressurized end.
 9. A mine roof support according to claim 6 wherein the nonpressurized ends of the cylinders are partially filled with liquid to limit the travel of the piston.
 10. A mine roof support according to claim 1 wherein the leg aligning device has associated with it a bolt arrangement to adjust the freestanding position of the leg.
 11. A mine roof support according to claim 7 wherein there are provided stop pins or like abutments to limit the travel of the pistons, these abutments being adjustable mounted in the cylinder wall at the nonpressurized end. 